The ordinary cartridge heater of the general class here concerned with comprises an elongate tubular metal case in which an elongate resistance wire is arranged. The resistance wire is supported in electric insulated relationship with the case by a compacted filler of granular dielectric material within the case and about the wire. The ends of the sheath are suitably plugged and sealed. The means plugging at least one end of the case is established of dielectric material through which one or a pair of elongate flexible jacketed power lines project. The inner ends of the power lines are electrically connected with related ends of the resistance wire. The outer ends of the power lines project freely from the plug or plugs and from their related ends of the case and extend to a suitable power supply.
Cartridge heaters of the general character here concerned with are used in a multitude of different environments. In many environments, it is necessary that the power lines be suitably shedded and protected. In such instances, it is common practice to engage or arrange the power lines for the heaters within elongate, flexible, tubular, braided metal sheaths, that is, within that form of flexible tubular sheathing which is braided of a multiplicity of fine, wire filaments. The most common braided sheathing is such that it can be extended or shortened longitudinally to a notable extent by the application of axially directed tensile and compressive forces and is such that its diametric extent is notably decreased or increased when it is extended or shortened longitudinally.
When the power lines of cartridge heaters are engaged within and protected by braided metal sheathing such as described above, it is common practice to simply slide and advance the sheaths longitudinally of the power lines so that the ends of the sheaths related to the heaters stop against and loosely engage the ends of the heaters. In such relationship of parts, the sheaths are subject to sliding longitudinally of the power lines and out of that position where they afford the protection sought to be afforded thereby. In order to prevent displacement of the sheaths, some of those working in the heater art have used various cements and the like to secure or fix the opposing ends of the heaters and the sheaths together. While such practices have met with varying degrees of success, use thereof has been avoided whenever possible since the time, labor and resulting costs in utilizing them is substantial and materially increases the costs of the resulting heater assemblies.
Still further, to the best of my knowledge and belief, those means which have been provided or utilized by the prior art to secure braided metal sheaths to or with related ends of cartridge heaters have afforded inadequate support for the end portions of the sheaths and their adjacent end portions of the power lines. The sheaths and power lines are subject to flexing excessively at their junctions with their related heaters with resulting premature hardening and breaking of the junctions.